Titanium dioxide (TiO₂) crystals are the most widely investigated photocatalysts. The performance of TiO₂ photocatalysts is sensitively affected by their surface atomic structures and surface electronic structures. Controlling the shapes of TiO₂ is becoming an important and popular strategy to tune the surface atomic structures and electronic structures so that an optimal performance can be reached. The chapter presents the, latest development in controllable synthesis of anatase TiO₂ with well-defined facets and their unusual photocatalytic properties.

Gang Liu;会明 成

2012-10-31

Yongqiang Yang;Gang Liu;John T.S. Irvine;会明 成

Advanced Materials

2016-7-27

Flowerlike Si-doped AlN nanoneedle array is grown from cobalt particles seeded on Si substrate by evaporating Al Cl4 and Si Cl4 in N H3 atmosphere. The nanoneedles are several microns in length, and their base and tip diameters are in the range of 50-150 and 5-30 nm, respectively. Field emission (FE) measurements show that the Si-doped AlN nanoneedle array has a low turn-on field (∼1.8 Vμm) and a high field enhancement factor (∼3271), indicating that it is a promising candidate for FE applications. In addition, this catalyst-seeded and Si-doped method may facilitate the development of efficient AlN nanostructure FE devices.

Y. B. Tang;H. T. Cong;Z. M. Wang;会明 成

Applied Physics Letters

2006

The influence of electron (hole) doping on the electronic structure of metallic single-walled carbon nanotubes (m-SWCNTs) is discussed by first principles calculations. The lattice constant c along the nanotube axis of m-SWCNTs (an (8, 8) armchair and a (12, 0) zigzag SWCNT, as examples) is calculated as a function of the Fermi energy. We find that the lengths of c for both sample nanotubes remain unchanged when the Fermi level changes between the first pair of van Hove singularities (VHS) states, while c decreases with increasing or decreasing Fermi level beyond that region. The decrease in c results in a decrease of the C-C bond length parallel to the tube axis (B _A), while it increases the C-C bond length perpendicular to the tube axis (B_R). By studying the energy separation (E11M) between the first pair of VHS states, we also find that E11M shows a similar behavior to those shown by c with changing Fermi level. Our study gives theoretical support for the optical properties of CNTs that are observed by electron/hole doping.

Li Chang Yin;会明 成;Riichiro Saito;Mildred S. Dresselhaus

Carbon

2011-11

Dong Chen;Lian Chen;Shi Liu;De Min Chen;会明 成;Chang Xiang Ma;Long Bao Wang

Zhongguo Youse Jinshu Xuebao/Chinese Journal of Nonferrous Metals

2003-8

Two-dimensional (2D) transition metal dichalcogenides (TMDCs) have attracted great attention due to their physical and chemical properties that make them promising in electronics and optoelectronics. Because of the difficulties in controlling concentrations of solid precursors and spatially nonuniform growth dynamics, it is challenging to grow 2D TMDCs over large areas with good uniformity and reproducibility so far, which significantly hinders their practical use. Here we report a vertical chemical vapor deposition (VCVD) design with gaseous precursors to grow monolayer TMDCs with a uniform density and high quality over the whole substrate and with excellent reproducibility. Such a gaseous VCVD design can well control the three key parameters in TMDC growth, including precursor concentration, gas flow, and temperature, which cannot be done in a currently widely used horizontal CVD system with solid precursors. Statistical results show that VCVD-grown monolayer TMDCs including MoS₂ and WS₂ are of high uniformity and quality on substrates over centimeter size. We also fabricated multiple van der Waals heterostructures by one-step transfer of VCVD-grown TMDCs, owning to their good uniformity. This work sheds light on the growth of 2D materials with high uniformity on a large-area substrate, which can be used for the wafer-scale fabrication of 2D materials and their heterostructures.

Lei Tang;Tao Li;Yuting Luo;Simin Feng;Zhengyang Cai;Hang Zhang;Bilu Liu;会明 成

ACS Nano

2020

Carbon fiber (CF) reinforced carbon-silicon carbide (C/C-SiC) composites are one of the most promising lightweight materials for re-entry thermal protection, rocket nozzles and brake discs applications. In this paper, a novel sandwich-structured C/C-SiC composite, containing two exterior C/SiC layers, two gradient C/C-SiC layers and a C/C core, has been designed and fabricated by two-step electromagnetic-coupling chemical vapor infiltration (E-CVI) for a 20-hour deposition time. The cross-section morphologies, interface microstructures and SiC-matrix growth characteristics and compositions of the composites were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD), respectively. Microstructure characterization indicates that the SiC growth includes an initial amorphous SiC zone, a gradual crystallization of SiC and grow-up of nano-crystal, and a columnar grain region. The sandwich structure, rapid deposition rate and growth characteristics are attributed to the formation of thermal gradient and the establishment of electromagnetic field in the E-CVI process. The composite possesses low density of 1.84 g/cm³, high flexural strength of 325 MPa, and low linear ablation rate of 0.38 μm/s under exposure to 5-cycle oxyacetylene flame for 1000 s at ~1700 °C.

Chenglong Hu;Wenhu Hong;Xiaojing Xu;Sufang Tang;Shanyi Du;会明 成

Scientific Reports

2017-12-1

Extensive research on two-dimensional (2D) materials has triggered the renaissance of an old topic, that is, the intercalation and exfoliation of layer materials. Such top-down exfoliation produced 2D materials and their dispersions have several advantages including low cost, scalable production capability, solution processability, and versatile functionalities stemming from the large number of species of layer materials, and show promising potential in many applications. In recent years, many new methods have been developed for exfoliating layer materials to 2D materials for different application purposes. In this review the different exfoliation approaches are first systematically analyzed from the viewpoint of methodology, and the advantages and disadvantages of each method are compared. Second, the assembly of exfoliated 2D materials into macrostructures by solution-based techniques is summarized. Third, the state-of-the-art applications of 2D material dispersions and their assemblies in electronics and optoelectronics, electrocatalysis, energy storage, etc., are discussed. Finally, insights and perspectives on current research challenges and future opportunities regarding the exfoliation and applications of 2D materials in dispersions are considered.

Xingke Cai;Yuting Luo;Bilu Liu;会明 成

Chemical Society Reviews

2018-8-21

TiF₃ shows a superior catalytic effect over TiCl₃ in improving the hydrogen sorption kinetics of MgH₂. Combined phase analysis and microstructure characterization suggest that both titanium halide additives react with host MgH₂ in a similar way. However, systematic X-ray photoelectron spectroscopy studies reveal that the incorporated fluorine (F) differs significantly from its analog chlorine (Cl) in terms of bonding state. The asymmetry of F 1s spectra and the sputtering-induced peak shift suggest that, in addition to the Mg-F bond, a new Ti-F-Mg bonding is formed in the TiF₃-doped MgH₂. In contrast, only one stable binding state of Cl is identified in the form of MgCl₂ for the TiCl₃-doped MgH₂. In combination with the designed experiments, these findings suggest that the generation of active F-containing species may be responsible for the advantage of TiF₃ over TiCl₃ in improving both the absorption and desorption kinetics of MgH₂. Fundamentally, it emphasizes the functionality of F anion in tuning the activity of compound catalyst.

L. P. Ma;X. D. Kang;H. B. Dai;Y. Liang;Z. Z. Fang;P. J. Wang;P. Wang;会明 成

Acta Materialia

2009-4

Revealing the key factors of controlling the reduction and oxidation half reactions of photocatalysis is necessary in order to obtain the implications for designing and developing efficient photocatalysts. In this work, boron-doped TiO₂ microspheres consisting of rutile nanorods with the top reactive {111} facets were synthesized by the acidic hydrolysis of TiB₂. The thermal diffusion of boron from the inner to surface part of the microspheres results in switching of the preference from photocatalytic H₂ evolution to O₂ evolution. This switching is caused by the downward shift of surface band edges with the incorporation of boron in surface.

Ting Ting Wu;Ying Peng Xie;Li Chang Yin;Gang Liu;会明 成

Journal of Physical Chemistry C

2015-1-8